It is Oracle best practice for all of the different instances to write archive and redo to shared storage. Delphix will also require that all datafiles and archivelogs be located on storage shared by all of the cluster nodes. The vast majority of RAC installations are configured this way to enable easy recoverability. For RAC VDBs, all storage is within Delphix, so all of the datafiles and archivelogs will already be using shared storage.